Hypertropia is a condition of misalignment of the eye

Human eye

The human eye is an organ which reacts to light for several purposes. As a conscious sense organ, the eye allows vision. Rod and cone cells in the retina allow conscious light perception and vision including color differentiation and the perception of depth...

s (strabismus

Strabismus

Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...

), whereby the visual axis of one eye is higher than the fellow fixating eye.
Hypotropia is the similar condition, focus being on the eye with the visual axis lower than the fellow fixating eye.
Dissociated Vertical Deviation

Dissociated Vertical Deviation

Dissociated Vertical Deviation is an ocular condition which occurs in association with a squint, typically Infantile Esotropia.- Mechanism :...

 is a special type of hypertropia leading to slow upward drift of one or rarely both eyes, usually when the patient is inattentive.

Etiology

Hypertropia may be either congenital or acquired, and misalignment is due to imbalance in extraocular muscle function. The superior rectus, inferior rectus, superior oblique, and inferior oblique muscles affect the vertical movement of the eyes. These muscles may be either paretic, restrictive (fibrosis) or overactive effect of the muscles. Congenital cases may have developmental abnormality due to abnormal muscle structure, usually muscle atrophy / hypertrophy or rarely, absence of the muscle and incorrect placement.
Specific & common causes include:

• Superior Oblique Palsy / Congenital fourth nerve palsy
  Congenital fourth nerve palsy
  Congenital fourth nerve palsy is a condition present at birth characterized by a vertical misalignment of the eyes due to a weakness or paralysis of the superior oblique muscle....
  
  
• Inferior Oblique overaction
• Brown's syndrome
  Brown's syndrome
  Brown's syndrome is a rare eye disorder characterized by defects and errors in eye movement. The disorder may be congenital , or secondary...
  
  
• Duane's Retraction Syndrome
• Double elevator palsy
• Fibrosis of rectus muscle in Graves Disease
  Graves-Basedow disease
  Graves' disease is an autoimmune disease where the thyroid is overactive, producing an excessive amount of thyroid hormones...
  
   (most commonly inferior rectus is involved)
• Surgical trauma to the vertical muscles (e.g. during scleral buckling surgery
  Scleral buckle
  A scleral buckle is one of several ophthalmologic procedures that can be used to repair a retinal detachment. Retinal detachments are usually caused by retinal tears, and a scleral buckle can be used to close the retinal break....
  
   or cataract surgery causing iatrogenic trauma to the vertical muscles).

Sudden onset hypertropia in a middle aged or elderly adult may be due to compression of the trochlear nerve

Trochlear nerve

The trochlear nerve is a motor nerve that innervates a single muscle: the superior oblique muscle of the eye....

 and mass effect from a tumor, requiring urgent brain imaging using MRI to localise any space occupying lesion. It could also be due to infarction of blood vessels supplying the nerve, due to diabetes and atherosclerosis.

Associated defects

Refractive errors such as hyperopia

Hyperopia

Hyperopia, also known as farsightedness, longsightedness or hypermetropia, is a defect of vision caused by an imperfection in the eye , causing difficulty focusing on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance...

 and Anisometropia

Anisometropia

Anisometropia is the condition in which the two eyes have unequal refractive power; that is, are in different states of myopia , hyperopia or in the extreme, antimetropia , the unequal refractive states cause unequal rotations thus leading to diplopia and asthenopia.Anisometropia can adversely...

 may be associated abnormalities found in patients with vertical strabismus.
The vertical miscoordination between the two eyes may lead to

• Strabismic amblyopia
  Amblyopia
  Amblyopia, also known as lazy eye, is a disorder of the visual system that is characterized by a vision deficiency in an eye that is otherwise physically normal, or out of proportion to associated structural abnormalities of the eye...
  
  , (due to deprivation / suppression of the deviating eye)
• cosmetic defect (most noticed by parents of a young child and in photographs)
• Face turn, depending on presence of binocular vision in a particular gaze
• diplopia
  Diplopia
  Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...
  
   or double vision - more seen in adults (maturity / plasticity of neural pathways) and suppression mechanisms of the brain in sorting out the images from the two eyes.
• Cyclotorsional deviation of the eyes (rotation around the visual axis), particularly when the root cause is an oblique muscle paresis causing the hypertropia.

Treatment

In general, strabismus can be approached and treated with a variety of procedures. Depending on the individual case, treatment options include:

• Correction of refractive errors by Glasses
• Prism therapy (if tolerated, to manage diplopia)
• Patching (mainly to manage amblyopia
  Amblyopia
  Amblyopia, also known as lazy eye, is a disorder of the visual system that is characterized by a vision deficiency in an eye that is otherwise physically normal, or out of proportion to associated structural abnormalities of the eye...
  
   in children and diplopia in adults)
• Botulinum Toxin Botox injection
• Surgical correction

Surgical correction of the hypertropia is desired to achieve binocularity, manage diplopia

Diplopia

Diplopia, commonly known as double vision, is the simultaneous perception of two images of a single object that may be displaced horizontally, vertically, or diagonally in relation to each other...

 and/or correct the cosmetic defect. Steps to achieve the same depend on mechanism of the hypertropia and identification of the offending muscles causing the misalignment. Various surgical procedures have been described and should be offered after careful examination of eyes, including a detailed orthoptic examination focussing on the disturbances in ocular motility and visual status. Specialty fellowship trained pediatric ophthalmologists

Pediatric ophthalmology

Pediatric ophthalmology is a sub-speciality of ophthalmology concerned with eye diseases, visual development, and vision care in children.-Training:...

 and strabismus

Strabismus

Strabismus is a condition in which the eyes are not properly aligned with each other. It typically involves a lack of coordination between the extraocular muscles, which prevents bringing the gaze of each eye to the same point in space and preventing proper binocular vision, which may adversely...

 surgeons are best equipped to deal with these complex procedures.

See also

• List of eye diseases and disorders
• List of systemic diseases with ocular manifestations